1. Field of the Invention
The present invention relates to an automobile rear body structure.
2. Description of the Background Art
Generally, an automobile is designed to have a luggage compartment space defined in a rear body thereof. In automobile design techniques, it is one of critical factors to ensure a wide luggage compartment space in view of providing enhanced utility. In a design process for increasing a luggage compartment space, it is required to give further consideration to ensuring adequate body rigidity. That is, an automobile rear body structure has to be designed to satisfy the need for increasing a luggage compartment space while ensuring adequate body rigidity. As typical automobile rear body structures, there has been known one type as disclosed, for example, in Japanese Patent Laid-Open Publication No. 2002-29457.
In the automobile rear body structure disclosed in the Japanese Patent Laid-Open Publication No. 2002-29457, a pair of rear side members as one skeletal frame constituting an automobile body are disposed to extend a frontward/rearward or longitudinal direction of the automobile body, and a rear floor panel is joined along respective top edges of the rear side members. An underfloor box for use as a spare tire storage or a sub-trunk is formed in a space above the rear floor panel. Further, a cross member as another skeletal frame constituting an automobile body is joined to respective rear ends of the rear side members in a front lower end region thereof in such a manner as to be located in a rearward and upward position relative to the rear side members in its entirety. This cross member is disposed to extend in a width or lateral direction of the automobile body so as to define a rear end of the underfloor box. The cross member consists of a rear end cross panel and a rear panel each extending in the lateral direction. The rear end cross panel and the rear panel are joined together at their front lower ends and at their rear upper ends, so that the cross member has a closed section defined therebetween. A shock absorbing member is attached to each of the rear ends of the rear side members. The shock absorbing member is designed to absorb an impact force acting thereon through a bumper disposed at a rearward position relative to the shock absorbing member, during a rear-impact vehicle collision.
FIG. 5 is a fragmentary perspective view shows a luggage compartment space in a rear body of a conventional automobile (hatchback type). FIG. 6 is a sectional view of a rear end cross member 55, taken along the line D-D in FIG. 5. The conventional rear body structure will be described below with reference to FIGS. 5 and 6. A rear floor pan 50 is disposed in the luggage compartment space to define a bottom thereof. This rear floor pan 50 is supported by a pair of rear side frames 60 each of which is a frame member extending in a frontward/rearward or longitudinal direction of the automobile body. The rear floor pan 50 has opposite lateral edges each cut off in conformity to a shape of a corresponding one of a pair of laterally opposed wheelhouse inner panels 51 and joined to the corresponding wheelhouse inner panel 51. The rear floor pan 50 is formed with a concave portion 53 serving as a spare tire storage for storing a spare tire therein.
The rear end cross member 55 is disposed to extend along a width or lateral direction of the automobile body. This rear end cross member 55 is joined to respective rear ends of the rear side frames 60 and along a rear edge of the rear floor pan 50. The rear end cross member 55 has opposite lateral ends each connected to a corresponding one of a pair of rear pillars 54. A striker S engageable with a latch (not shown) of a rear gate (not shown) is attached on a laterally central region of a top surface of the rear end cross member 55.
As shown in FIG. 6, the rear end cross member 55 consists of a rear panel 56 and a front panel 57 which define a closed section therebetween. The front panel 57 extends downward from its closed-section-defining portion to form a flange. Each of the rear ends 60a of the rear side frame 60 is joined to the flange. Further, a rear bumper reinforcing member and a rear bumper are attached to the flange from the rear side thereof.
In some types of automobiles, such as hatchback type, it is proposed to design a rear end of an automobile body to protrude rearward in a substantially circular arc shape in top plan view, like the tail of an insect (hereinafter referred to as “rear protrusion type”). This sort of design is getting attention as one technique for improving the aesthetic quality in external appearance of an automobile.
However, the conventional rear protrusion type automobile body structure has a problem that, while a certain space is created between a line connecting respective rear ends of a pair of rear side frames, and a rear bumper reinforcing member attached at a rearward position relative to the rear side frames, the created space is left as a dead space or is not effectively utilized.